You will also need to consider the weight, not just for the floor, but also for the framing suspending the tank (presumably at eye level). Based upon the dimensions you supplied (I used the larger of each) you are looking at around 1080 liters of water. A liter of water weights about 1 kilo, so you need to support 1080 kilos (approx. 2380 pounds) of just water. Add in the weight of the aquarium, gravel, etc.